Micromirror array lens with encapsulation of reflective metal layer and method of making the same

ABSTRACT

The present invention provides a micromirror array device specially Micromirror Array Lens device structure and method for making the same. By introducing a sub coating layer and an over coating layer with a high reflective metal layer, the reflective layer of the micromirrors is protected from environmental circumstances, oxidation, degradation, acid, base, and galvanic corrosion of the micro-mechanical structures. Also the new coating structure enhances the performance of the Micromirror Array Lens by reducing degradation of the reflectivity of the metal layer, by providing anti-reflection in the optically non-effective area, and by protecting the micro-mechanical structures.

FIELD OF INVENTION

The present invention relates to fabrication of micromirror arraydevice, more specifically, Micromirror Array Lens fabrication andstructure.

BACKGROUND OF THE INVENTION

Since the Digital Micromirror Device (DMD) was invented, many an opticalmicromirror device has been introduced. Micromirror related devices areusually light reflecting and light modulating devices. Especiallycontrolling light and having a good quality of reflectivity is essentialto the device as well as the operation of the micromirror devices. Toimprove the optical quality of the micromirror device, scientists andengineers have been making efforts for developing new optical coatingsand new structures for micromirror devices.

Hornbeck discloses a micromirror array device with metal layer made ofaluminum alloy in U.S. Pat. No. 5,083,857. Since the micromirror arraywas made by the aluminum alloy, the micromirror array device has areflectivity of metal. It has a good performance of light reflecting andmodulating. Even though aluminum alloy has a high reflectivity, themetal surface is degraded by oxidation. Since the metal layer wasexposed to the environments, the reflectivity of the micromirror wasslowly degraded by oxidation.

To enhance the optical properties of the micromirror device,anti-reflective coatings are also investigated. Some example can befound in the U.S. Pat. No. 6,282,010 to Sulzbach, and the U.S. Pat. No.7,009,745 to Miller. In those patents, the structures under thereflective surface are coated with anti-reflective materials. Since thestructure of the micromirror device was made with metal or metal alloy,the structure itself has a relatively high reflectivity. The residuallight reflected from the metal surface other than reflective mirrorsurface made serious problems for generating images with high resolutionand high quality. The anti-reflection coating for the structure enhancedthe optical quality of the micromirror device. But the enhancement wasnot enough and the process for anti-reflective coating was complex anddifficult.

By introducing wafer bonding and transparent substrates, a differentstructure for micromirror device was disclosed by Huibers in the U.S.Pat. No. 5,835,256. The device has a better protection for reflectivemirror surface, but the fabrication of the device becomes considerablydifficult with fabrication on the transparent wafer and wafer bonding oftwo different wafers. One more problem is that this structureexperiences a thermal degradation of the reflectivity.

More recently, another micromirror array device was disclosed in U.S.Pat. No. 6,970,284 to Kim, U.S. Pat. No. 7,031,046 to Kim, U.S. Pat. No.6,934,072 to Kim, U.S. Pat. No. 6,934,073 to Kim, U.S. Pat. No.6,999,226 to Kim. The Micromirror Array Lens acts as a variable focuslens by controlling micromirrors in the Micromirror Array Lens. Themicromirrors in the Micromirror Array Lens need a good quality ofoptical coating as well as protection for the micro-mechanicalstructures. Good quality of optical coating is closely related to theperformance of the Micromirror Array Lens. Since the device acts as alens, the high reflective surface of the micromirrors is essential tothe device. Also the protection of the micro-mechanical structure is amust to have precise motion control of the micromirror device.

In the present invention, a new structure and method for enhancingoptical properties as well as protection of the micro-mechanicalstructures. The present invention is dedicated to solve the followingproblems: oxidation of the metal coating, degradation of the reflectivecoating layer, protection of micro-mechanical structures and reflectivesurface from the acid and base, protection of reflective surface fromsevere environments, providing the anti-reflective coating for opticallynon-effective area, providing protective layer for reflective surface,and simplifying the process of fabrication.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a micromirror arraydevice especially Micromirror Array Lens and a method for making thesame. While fabricating the micromirror array device, there remain lotsof obstacles for having a good quality of operation. Especiallyproviding a good optical quality is very important in making micromirrorarray device. The present invention provides a Micromirror Array Lenswith special coating structures. By introducing a sub coating layer andan over coating layer with a high reflective metal layer, thereflectivity of the micromirrors in the Micromirror Array Lens ispreserved and protected from environmental circumstances, oxidation,degradation, acid, base, and galvanic corrosion of the micro-mechanicalstructures.

The properties of the Micromirror Array Lens and its structures can befound in U.S. Pat. No. 6,970,284 to Kim, U.S. Pat. No. 7,031,046 to Kim,U.S. Pat. No. 6,934,072 to Kim, U.S. Pat. No. 6,934,073 to Kim, U.S.Pat. No. 6,999,226 to Kim, U.S. Pat. No. 7,095,548 to Cho, US PatentPublication No. 20050275929 A1, US Patent Publication No. 20050280883A1, US Patent Publication No. 20060012852 A1, US Patent Publication No.20050264870 A1, US Patent Publication No. 20060152792 A1, US PatentPublication No. 20060203358 A1, US patent application Ser. No.11/426,565 filed on Jun. 26, 2006, and U.S. patent application Ser. No.11/463,875 filed on Aug. 10, 2006, all of which are hereby incorporatedby reference.

The Micromirror Array Lens of the present invention comprises aplurality of micromirrors. Each micromirror in optically effective areacomprises a substrate with at least one electrode and at least oneactuation element, a micromirror structure, a sub coating layer, a metallayer, and an over coating layer. The effective area is the area wherethe actual focusing of the Micromirror Array Lens is performed. Bychanging the motion of the micromirror in the effective area, theMicromirror Array Lens can change its focal length, optical axis, andother focusing properties.

The substrate has at least one electrode to provide actuation force formicromirror motion. The actuation elements make micromirror motioncontrolled by electrostatic force induced between the electrodes in thesubstrate and the micromirror structure. All the elements which arerelated with the motion of the micromirror can be actuation elements.The micromirror structure has rotational and/or translational motionscontrolled by the actuation elements. The sub coating and the overcoating layer encapsulate the metal layer to prevent the metal layerfrom oxidation and to prevent the micromirror structure and theactuation elements from galvanic corrosion. The metal layer makes themicromirror structure have high reflectivity. The encapsulation of themetal layer considerably reduces degradation of reflectivity by themetal layer. The sub coating and the over coating layer provide goodprotective layers for the metal layer.

The shape of the micromirrors can be varied with geometry of theMicromirror Array Lens. The micromirrors in the effective area have ashape selected from the group consisting of fan, rectangular, square,hexagonal, and triangular shapes. With an optical geometry with arotational symmetry, a fan shape for micromirrors is a good choice foreffective fabricating the Micromirror Array Lenses. For an opticalsystem with an axis-symmetry, micromirrors with rectangular or squareshapes can be selected to have a proper geometry of the optical system.The hexagonal and triangular shape micromirrors are also used forsystems with the axis-symmetry, especially with three-fold axissymmetry. Hexagonal micromirrors can be used for highly dense system.Anyway, the selection of the micromirror shapes is highly dependent onthe optical system geometry and the devices.

The substrate has at least one electrode, usually a plurality ofelectrodes for providing actuation force for micromirror motion. Eachelectrode is used for generating motion for micromirror. Sometimesgroups of electrodes are used for micromirror motion. For controllingthe micromirror, a control circuitry should be constructed. Thesubstrate comprises a control circuitry constructed by usingsemiconductor microelectronics technologies such as MOS and CMOStechnologies. By providing semiconductor microelectronics, theMicromirror Array Lens can have high flexibility in motion control withconvenience.

To build electrostatic force between the electrodes and the actuationelements or micromirror structure, the electrodes should have adifferent electric potential from the electric potential of theactuation elements or the micromirror structure. To prevent frompossible electric contact between the structures and elements, theelectrodes are protected by passivation layer. The passivation layerprevents the electrodes from possible electric contact or problems withother structures in the micromirror structure. The passivation layer canbe built with silicon oxide or low-stressed silicon nitride (LSN) sincethey have high electrical resistance and easy accessibility forfabrication.

To have a function as a Micromirror Array Lens, the micromirror arrayfor Micromirror Array Lens should satisfy two conditions to form a goodlens. One is the convergence condition that every light should beconverged into a focal point. The other is the phase matching conditionthat the phase of the converged light should be the same. In aconventional lens, the phase matching condition is that all the lightpassing through a lens should have the same optical path length to thefocal point. But the Micromirror Array Lens arranged in a flat surfaceuses the periodicity of the light to satisfy the phase matchingcondition. Since the same phase condition occurs periodically, the phasematching condition can be satisfied even though the optical path lengthis different. Each micromirror in the Micromirror Array Lens can becontrolled independently to satisfy the phase matching condition and theconvergence condition.

Only after satisfying the convergence and the phase matching conditions,the Micromirror Array Lens can build a lens with an optical surfaceprofile. An optical surface profile is the surface shape of themicromirror array which meets the lens conditions of convergence andphase matching. Each micromirror in the effective area is independentlycontrolled to form at least an optical surface profile. The MicromirrorArray Lens has a plurality of optical surface profiles to have avariable focusing property. By changing the optical surface profile, theMicromirror Array Lens can change its focal length, optical axis, andfocusing properties. The Micromirror Array Lens can be a variablefocusing lens having lots of optical profiles.

To have simplicity in control circuitry, the Micromirror Array Lens canbe built so that the micromirrors in the effective area are controlledby a common input signal to the electrodes to form an optical surfaceprofile. With this method, the Micromirror Array Lens can be digitallyor discretely controlled to have an optical surface profile withcorresponding optical properties. Also the number of the inputs can bereduced by using common input signal down to the number of opticalsurface profiles. To control a certain amount of the optical surfaceprofiles, only the same number of the electrical inputs is needed. Alsothe operating circuitry becomes extremely simple.

The sub coating and the over coating layer encapsulate the metal layerto prevent the metal layer from oxidation and to prevent the micromirrorstructure and the actuation elements from galvanic corrosion. Theencapsulated metal layer is protected by the sub coating and the overcoating from degradation of reflectivity and also from acid, base, orsevere environments. The sub coating layer is deposited on themicromirror structure with material selected from the group consistingof silicon oxide (SiO₂), aluminum oxide (Al₂O₃), magnesium oxide (MgO),titanium oxide (TiO₂), cesium oxide (CeO₂), silicon nitride (Si₃N₄),titanium nitride (TiN), magnesium fluoride (MgF₂), zinc sulfide (ZnS),zinc selenide (ZnSe), polycarbonate, polyester, polyethylenenaphthalate, and fluoropolymer.

To prevent the micromirror structure and the actuation elements fromgalvanic corrosion, the sub coating layer prevents the metal layer fromelectrical contacting with micromirror structure. Since the galvaniccorrosion can only occur if the dissimilar metals are in electricalcontact. When the dissimilar metals are insulated from each other bysuitable plastic strips, washers or sleeves, the galvanic corrosioncannot occur. Thus the sub coating layer prevents the micromirrorstructure and the actuation elements from galvanic corrosion byelectrically separating the micromirror structure and the metal layer.For micromirror array devices with electrostatic force actuation, theelectrical separation is especially important. The sub coating materialshould be highly electrically insulating and also consistent with thefabrication processes. To have sufficient electrical separation andoptical properties, the thickness of the sub coating layer should becontrolled to have between 20 nm and 500 nm preferably 100 nm.

The metal layer is made of material selected from the group consistingof silver (Ag), aluminum (Al), gold (Ag), nickel (Ni), chromium (Cr),and platinum (Pt) for the micromirror structure to have highreflectivity. The thickness of the metal layer is controlled to havebetween 20 nm and 1000 nm preferably 100 nm. The thickness should becontrolled to have high reflectivity of the micromirrors in theMicromirror Array Lens. Also the material of the metal layer should beselected by considering the required reflectivity, operating wavelength,operating environment, and others. Also since the metal layer is easy tobe attacked from acid or base or other environmental reasons, the metallayer should be protected from them. In the present invention, the subcoating and the over coating provide a strong protection for the metallayer from oxidation, acid, base and galvanic corrosion by encapsulatingthe metal layer. The over coating layer and the sub coating layerprevent the metal layer from oxidation by encapsulating the metal layer.The over coating layer and the sub coating layer protect the metal layerfrom acid or base to maintain reflectivity of the micromirrors byencapsulating the metal layer. The degradation of the reflectivity isconsiderable reduced by encapsulation of the metal layer by the subcoating layer and the over coating layer. One more thing is that theover coating layer and the sub coating layer protect the metal layerfrom etchants while removing sacrificial layer or layers of themicro-mechanical structure. Usually while removing sacrificial layer orlayers, a strong acid or base such as fluoric acid is applied todissolve the sacrificial layers made of such as silicon oxide.

The over coating layer provides a protection for metal layer from theoperating environments. Since the metal layer should have highreflectivity, the thickness of the over coating layer should becontrolled to maximize reflectivity of the metal layer. The maximizedreflectivity enhances the performance of the Micromirror Array Lens. Thethickness of the over coating layer is controlled to have between 20 nmand 500 nm preferably 100 nm. Since the over coating layer is directlyexposed to the operating environment, the thickness of the over coatinglayer is more important than that of the sub coating layer, especiallyto control the reflectivity of the micromirrors.

The sub coating layer is deposited on the micromirror structure withmaterial selected from the group consisting of silicon oxide (SiO₂),aluminum oxide (Al₂O₃), magnesium oxide (MgO), titanium oxide (TiO₂),cesium oxide (CeO₂), silicon nitride (Si₃N₄), titanium nitride (TiN),magnesium fluoride (MgF₂), zinc sulfide (ZnS), zinc selenide (ZnSe),polycarbonate, polyester, polyethylene naphthalate, and fluoropolymer.

The Micromirror Array Lens further comprises an optically non-effectivearea which is other than the controlled micromirror area. Since thestructure in the non-effective area does not need actuation parts, thestructure of the non-effective area is somewhat different from that ofeffective area. The non-effective area comprises a substrate, at leastone dummy structure, a sub coating layer, and an over coating layer. Thesub coating and the over coating layers are fabricated together with thelayers in the micromirrors in the effective area.

Since the Micromirror Array Lens is a fragile device, the micromirrorsshould be protected during the fabrication and the usage. To protect themicromirror structures in the optically effective area, the dummystructure is introduced and fabricated with the micromirror structures.The dummy structures protect the micromirrors in the effective area fromexternal perturbation. The external perturbation can be occurred duringfabrication of the Micromirror Array Lens and operation of theMicromirror Array Lens. The dummy structures enclose the effective areaand acts as a buffer area of the device. The dummy structures are alsofabricated with the micromirror structures or elements in the effectivearea.

To enhance the optical performance of the Micromirror Array Lens, thenon-effective area should not be optically active. The anti-reflectivecoating enhances the optical performance of the Micromirror Array Lens.Since the dummy structures do not have metal layer, the structures donot have high reflectivity, but still the dummy structures make effectson the optical quality. To enhance the optical performance, it is highlydesired that the non-effective area has as low reflectivity as possible.An anti-reflective coating for the non-effective area is one solution.By controlling the thickness of the exist layers for the micromirrors,the non-effective area can have anti-reflective coating. In thenon-effective area, two layers of sub coating and over coating layersare applied to the dummy structures. The total thickness of the subcoating and over coating layers can be controlled to haveanti-reflective coating properties. To provide anti-reflective coatingfor non-effective area along with protection of the metal layer is theone of main ideas and advantages of the present invention.

In the present invention, the method for fabricating the MicromirrorArray Lens is also provided. The method for fabricating the MicromirrorArray Lens comprises the steps of forming electrodes and controlcircuitry on a substrate, building micromirror actuation elements withsacrificial layer or layers, applying a micromirror structure layer,applying a sub coating layer to the micromirror structure, applying ametal layer to the sub coating layer on effective area, applying an overcoating layer, selectively etching the sub coating layer, the overcoating layer and the micromirror structure layer to make micromirrorstructures with coating layers, removing the sacrificial layers andreleasing the actuation elements and the micromirror structures. Themetal layer is encapsulated by the sub coating layer and the overcoating layer to prevent the metal layer from oxidation and to preventthe micromirror structures and the actuation elements from galvaniccorrosion. Also non-effective area can be made without extra process offabrication. The only differences are that the non-effective area doesnot have metal layer since it does not need high reflectivity and thatthe non-effective area does not have actuation elements. The dummystructures in the non-effective area are more likely the micromirrorstructures without actuation part. There are lots of advantages for themethod of the present invention. By applying the sub coating layer andthe over coating layer, the metal layer can be protected from severeenvironments, oxidation, degradation of reflectivity, acid, base, andgalvanic corrosion.

The sub coating and the over coating can provide optical properties tothe effective and non-effective area as much as protection to the metallayer. In the effective area, the thickness of the over coating layer iscontrolled to have high reflectivity along with the protection of themetal layer. And in the non-effective area, the over coating and the subcoating are combined together since there is no metal layer. The totalthickness of the sub coating and the over coating is controlled to haveanti-reflective property.

Also the coating layer and the micromirror structure can be etchedtogether. After depositing the micromirror structure together with dummystructure in the non-effective area, the sub coating layer is deposited.Next the metal layer is deposited with patterning the shape ofmicromirrors. The over coating layer is followed by the metal layer toencapsulate the metal layer with the sub coating layer. After all thelayers are deposited, the layers are patterned and etched. The etchingprocesses can be performed altogether with the same patterning process,which reduces the process of the fabrication considerably.

The Micromirror Array Lens of the present invention has advantages: (1)the high reflective metal layer is protected from oxidation; (2) thereflective metal layer is protected from acid or base; (3) thedegradation of the reflective metal layer is reduced; (4) themicro-mechanical structures are protected from galvanic corrosion; (5)the metal layer can have high reflectivity with protection; (6) thenon-effective area has anti-reflective coating to enhance opticalperformance; (7) anti-reflection and protection coating are depositedaltogether; (8) the coating layers and the micromirror structure can beetched together; (9) the process of fabrication is simple.

Although the present invention is briefly summarized, the fullunderstanding of the invention can be obtained by the followingdrawings, detailed description, and appended claims.

BRIEF DESCRIPTION OF THE FIGURES

While the appended claims set forth the features of the presentinvention with particularity, the invention, together with its objectsand advantages, may be best understood from the following detaileddescription taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 shows structure of a micromirror in a Micromirror Array Lens withsub coating and over coating layers altogether with the metal layer;

FIG. 2 shows structure of a micromirror in a Micromirror Array Lensbefore removing the sacrificial layers;

FIGS. 3A-3I shows fabrication process of the Micromirror Array Lens witheffective and non-effective area;

FIG. 4 illustrates an optical system of a Micromirror Array Lens havingan axis-symmetry;

FIG. 5 illustrates effective and non-effective area determined by theoptical geometry with an axis-symmetry.

FIG. 6 illustrates an optical system of a Micromirror Array Lens havingan rotational symmetry;

FIG. 7 illustrates effective and non-effective area determined by theoptical geometry with a rotational symmetry.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the structure of a micromirror with sub coating 17 and overcoating 19 layers altogether with the metal layer 18. The substrate 11has at least one electrode 12 to build electrostatic force between thesubstrate 11 and the micromirror structure 16. To control themicromirror motion, the corresponding electrode 12 for motion has anelectric potential different from the electric potential of themicromirror structure 16. The electrically charged structure makes thecapacitive force between the electrodes 12 and the micromirror structure16. To make micromirror motion, some structures work together and makeactuation force to the micromirror. The pillar structure 13 gives arigid rotational or translational center to the micromirror structure16. The flexible spring structure 14 connects the rigid bodies and themoving structures. The top electrode 15 gives enhancement on theelectrostatic force and on the structural stability. The pillarstructure 13, the flexible spring structure 14, the top electrode 15,and other components for actuation are the actuation components. Themicromirror structure 16 is built for the base of the micromirror motionand the reflective surface of the micromirror device. On top of themicromirror structure 16, the sub coating layer 17 is applied to buildinsulation between the micromirror structure 16 and the metal layer 18.The metal layer 18 lies on top of the sub coating layer 17 and giveshigh reflectivity to the micromirror structure 16. The micromirrorstructure 16 with high reflectivity plays a role of a high reflector,thus the micromirror array plays a role of a spatial light modulator.And then finally the over coating layer 19 is applied. The over coating19 is applied to encapsulate the metal layer 18 with the sub coatinglayer 17 and to prevent the exposure of the metal layer 18 direct to theoperational environment, oxidation, acid, base, or galvanic corrosion.

The sub coating 17 and the over coating layer 19 encapsulate the metallayer 18 to prevent the metal layer 18 from oxidation and degradation ofthe high reflectivity and also to prevent the micromirror structure 16and the actuation elements 13, 14, 15 from galvanic corrosion. Theencapsulated metal layer 18 is protected by the sub coating 17 and theover coating 19. The sub coating layer 17 and the over coating layer 19is deposited on the micromirror structure 16 with material selected fromthe group consisting of silicon oxide (SiO₂), aluminum oxide (Al₂O₃),magnesium oxide (MgO), titanium oxide (TiO₂), cesium oxide (CeO₂),silicon nitride (Si₃N₄), titanium nitride (TiN), magnesium fluoride(MgF₂), zinc sulfide (ZnS), zinc selenide (ZnSe), polycarbonate,polyester, polyethylene naphthalate, and fluoropolymer.

To prevent the micromirror structure 16 and the actuation elements 13,14, 15 from galvanic corrosion, the sub coating layer 17 prevents themetal layer 18 from electrical contacting with micromirror structure 16.Since the galvanic corrosion can only occur if the dissimilar metals arein electrical contact. Here in the present invention of the MicromirrorArray Lens, the micromirror structure 16 and the metal layer 18 are thedissimilar metals for possible galvanic corrosion. If the dissimilarmetals are insulated from each other by suitable plastic strips, washersor sleeves then galvanic corrosion cannot occur. Thus the sub coatinglayer 17 prevents the micromirror structure 16 and the actuationelements 13, 14, 15 from galvanic corrosion by electrically separatingthe micromirror structure 16 and the metal layer 18. The sub coating 17materials should be highly electrically insulating and also consistentwith the fabrication processes. While selecting the material for thecoatings 17, 19, these requirements should be considered.

To have sufficient electrical separation and optical properties, thethickness of the sub coating layer 17 should be controlled to havebetween 20 nm and 500 nm preferably 100 nm. The over coating layer 19provides a protection for metal layer 18 from the operatingenvironments. Since the metal layer 18 should have high reflectivity,the thickness of the over coating layer 19 should be controlled tomaximize reflectivity of the metal layer 18. The maximized reflectivityenhances the efficiency of the Micromirror Array Lens. The thickness ofthe over coating layer 19 is controlled to have between 20 nm and 500 nmpreferably 100 nm. Since the over coating layer 19 is directly exposedto the operating environment, the thickness of the over coating layer 19is more important than that of the sub coating layer 17, especially tohave high reflectivity of the micromirrors.

The metal layer 18 is made of material selected from the groupconsisting of silver (Ag), aluminum (Al), gold (Ag), nickel (Ni),chromium (Cr), and platinum (Pt) to have high reflectivity. Thethickness of the metal layer 18 is controlled to have between 20 nm and1000 nm preferably 100 nm. The thickness should be selected to have highreflectivity of the micromirrors. Also the material of the metal layer18 should be selected by considering the required reflectivity,operating wavelength, operating environment and others. Also since themetal layer 18 is easy to be attacked from acid or base or otherenvironmental reasons, the metal layer 18 should be protected. In thepresent invention, the sub coating 17 and the over coating 19 provide astrong protection for the metal layer 18 from oxidation, acid, base andgalvanic corrosion. The over coating layer 19 and the sub coating layer17 prevent the metal layer 18 from oxidation by encapsulating the metallayer 18. The over coating layer 19 and the sub coating layer 17 protectthe metal layer 18 from acid or base to maintain reflectivity of themicromirror by encapsulating the metal layer 18. One more thing is thatthe over coating layer 19 and the sub coating layer 17 protect the metallayer 18 from etchants while removing sacrificial layers. Usually whileremoving sacrificial layer, a strong acid or base such as fluoric acidis applied to dissolve the sacrificial layer such as silicon oxide.

FIG. 2 shows the structure of a micromirror in the Micromirror ArrayLens before removing the sacrificial layers 24. From the substrate 21,the micromirror in the Micromirror Array Lens is fabricated with layerby layer. The electrical circuitry and the electrodes for micromirrormotion generation are laid on top of the substrate 21. And then theactuation elements 22, 23, 25 are fabricated on the substrate 21 withelectrodes. The actuation elements are the pillar structure 22, theflexible spring structure 23, the top electrode 25, and etc. Theactuation elements 22, 23, 25 are built with the sacrificial layer 24 tomake the structure become layer by layer flat. Then the micromirrorstructure 26 is made with connection to the actuation elements 22, 23,25. And then the micromirror structure 26 has a high reflectivity bydepositing the metal layer 28. This metal layer 28 is encapsulated andprotected by the sub coating layer 27 and the over coating layer 29while releasing process for removing the sacrificial layer 24 and whilethe operation of the Micromirror Array Lens. Since the metal layer 28 isextremely reactive in some cases, the layer should be protected fromoxidation, degradation, acid, and base. This sub coating 27 and overcoating layers 29 enhance the durability of the optical coating made bythe metal layer 28, thus the Micromirror Array Lens.

The substrate 21 has at least one electrode, usually a plurality ofelectrodes for providing actuation force for micromirror motion. Eachelectrode is used for generating motion for micromirror. Sometimesgroups of electrodes are used for micromirror motion. The electricalcircuitry in the substrate 21 gives the controllability of themicromirror device. When the micromirror device becomes a micromirrorarray or a Micromirror Array Lens, the control circuitry becomes morecomplex. In a Micromirror Array Lens, the electrical control circuitryhas its controllability of each micromirror. For controlling themicromirrors in the Micromirror Array Lens, a control circuitry shouldbe constructed. The substrate 21 comprises a control circuitryconstructed by using semiconductor microelectronics technologies such asMOS and CMOS technologies. By providing semiconductor microelectronics,the Micromirror Array Lens can have high flexibility in motiongeneration with easy control.

To build electrostatic force between the electrodes and the actuationelements 22, 23, 25 or micromirror structure 26, the electrodes shouldhave a different electric potential from the electric potential of theactuation elements 22, 23, 25 or micromirror structure 26. To preventfrom the possible electric contact between the structures and elements,the electrodes are protected by passivation layer (not shown in thefigure). The passivation layer prevents the electrodes from possibleelectric contact with other structures 22, 23, 25, 26 in themicromirror. Passivation layer can be built with silicon oxide orlow-stressed silicon nitride since they have high electrical resistance.

Especially to build a micromirror array as a Micromirror Array Lens, themicromirror array should satisfy two conditions to form a good lens. Oneis the convergence condition that every light should be converged into afocal point. The other is the phase matching condition that the phase ofthe converged light should be the same. In a conventional lens, thephase matching condition is that all the light passing through a lensshould have the same optical path length to the focal point. But theMicromirror Array Lens arranged in a flat surface uses the periodicityof the light to satisfy the phase matching condition. Since the samephase condition occurs periodically, the phase matching condition can besatisfied even though the optical path length is different. Eachmicromirror in the Micromirror Array lens can be controlledindependently to satisfy the phase matching condition and theconvergence condition.

Only after satisfying the convergence and the phase matching conditions,the Micromirror Array Lens can build a lens with an optical surfaceprofile. An optical surface profile is the surface shape of themicromirror array which meets the lens conditions of convergence andphase matching. Each micromirror in the effective area is independentlycontrolled to form at least an optical surface profile. The MicromirrorArray Lens has a plurality of optical surface profiles to have avariable focusing property. By changing the optical surface profile, theMicromirror Array Lens can change its focal length, optical axis, andfocusing properties. The Micromirror Array Lens can be a variablefocusing lens having lots of optical profiles.

To have simplicity in control circuitry, the Micromirror Array Lens canbe built so that the micromirrors in the effective area are controlledby a common input signal to the electrodes to form an optical surfaceprofile. With this method, the Micromirror Array Lens can be digitallyor discretely controlled to have an optical surface profile withcorresponding optical properties. Also the number of the inputs can bereduced by using common input signal down to the number of opticalsurface profiles. To control a certain amount of the optical surfaceprofiles, only the same number of the electrical inputs is needed. Alsothe operating circuitry becomes extremely simple.

The motion of the Micromirror Array Lens is activated by applyingvoltages to the corresponding electrodes through the control circuitry.The motion can be made only after the releasing process by removing thesacrificial layer 24 or structures 22, 23, 25, 26 in the micromirrordevice.

FIGS. 3A-3I shows the fabrication process of micromirror device witheffective area 39A and non-effective area 39B. The method forfabricating the Micromirror Array Lens comprises the steps of formingelectrodes 31A, 31B and control circuitry on a substrate 31C, buildingmicromirror actuation elements 32A, 32B, 32C, 32D, 32E with sacrificiallayer or layers 37, applying a micromirror structure layer 33C, applyinga sub coating layer 34C to the micromirror structure layer 33C, applyinga metal layer 35 to the sub coating layer 34C on effective area 39A,applying an over coating layer 36C, selectively etching the sub coatinglayer 34C, the over coating layer 36C and the micromirror structurelayer 33C to make micromirror structures 33A, 33B with coating layers34A, 34B, 36A, 36B, removing the sacrificial layers 37 and releasing theactuation elements 32A, 32B, 32C, 32D, 32E and the micromirrorstructures 33A, 33B. The metal layer 35 is encapsulated by the subcoating layer 34A and the over coating layer 36A to prevent the metallayer 35 from oxidation and to prevent the micromirror structures 33A,33B and the actuation elements 32A, 32B, 32C, 32D, 32E from galvaniccorrosion. Non-effective area 39B can be made without extra process offabrication. The differences from the effective area 39A are that thenon-effective area 39B does not have metal layer 35 since it does notneed high reflectivity and that the non-effective area 39B does not haveactuation elements 32A, 32C, 32D, 32E. The dummy structures 33B are morelikely the micromirror structures 33A without actuation part. There arelots of advantages for the method of the present invention. By applyingsub coating layer 34A and over coating layer 36A, the metal layer 35 canbe protected from severe environments, oxidation, degradation, acid,base, and galvanic corrosion.

The sub coating 34A, 34B and the over coating 36A, 36B can provideoptical properties to the effective area 39A and non-effective area 39Bas much as protection to the metal layer 35. In the effective area 39A,the thickness of the over coating layer 36A is controlled to have highreflectivity along with the protection of the metal layer 35. And in thenon-effective area 39B, the over coating 36B and the sub coating 34B arecombined together since there is no metal layer. The total thickness ofthe sub coating 34B and the over coating 36B can be controlled to haveanti-reflective property of the Micromirror Array Lens in thenon-effective area 39B.

Also the coating layer 34C, 36C and the micromirror structure 33C can beetched together. After depositing the micromirror structure layer 33Cincluding micromirror structure 33A in the effective area 39A togetherwith dummy structure 33B in the non-effective area 39B, the sub coatinglayer 34C is deposited. Next the metal layer 35 is deposited withpatterning with the shape of micromirrors. The over coating layer 36C isfollowed by the metal layer 35 to encapsulate the metal layer 35 withthe sub coating layer 34C. After all the layers 33C, 34C, 35, 36C aredeposited, the layers 33C, 34C, 36C are patterned and etched. Theetching processes can be performed altogether with the same patterningprocess, which reduces the process of the fabrication considerably.

FIG. 3A shows the first step of building the Micromirror Array Lens,which is making the electrodes 31A, 31B on the substrates 31C. Thesubstrate 31C has at least one electrode 31A, 31B usually a plurality ofelectrodes 31A, 31B for providing actuation force for micromirrormotion. Each electrode 31A is used for generating motion formicromirror. Sometimes groups of electrodes 31A are used for micromirrormotion. For controlling the micromirror, a control circuitry should beconstructed. The substrate 31C comprises a control circuitry constructedby using semiconductor microelectronics technologies such as MOS andCMOS technologies. By providing semiconductor microelectronics, theMicromirror Array Lens can have high flexibility in motion with easycontrol.

In FIG. 3B, the fabrication of the actuation elements 32A, 32B, 32C,32D, 32E with sacrificial layers 37 are illustrated. To buildelectrostatic force between the electrodes 31A and the actuationelements 32A, 32B, 32C, 32D, 32E, or micromirror structure 33A, theelectrodes 31A should have a different electric potential from theactuation elements 32A, 32B, 32C, 32D, 32E or micromirror structure 33A.To prevent from the possible electric contact between the structures andelements 32A, 32B, 32C, 32D, 32E, 33A the electrodes 31A, 31B areprotected by passivation layer (not shown in the figure). Thepassivation layer prevents the electrodes 31A, 31B from possibleelectric contact with other structures in the Micromirror Array Lens.Passivation layer can be built with silicon oxide or low-stressedsilicon nitride since they have high electrical resistance.

After building the electrodes 31A, 31B with control circuitry on thesubstrate 31C, the actuation elements 32A, 32B, 32C, 32D, 32E are builtwith sacrificial layer 37. To make micromirror motion, some structureswork together and make actuation force to the micromirror. The pillarstructure 32A, 32B gives a rigid rotational or translational center tothe micromirror structures 33A. The flexible spring structure 32Cconnects the rigid bodies and the moving structures and also therestoration force to the system. The top electrode 32D gives enhancementon the electrostatic force and on the structural stability. The topelectrode 32D and the micromirror structure 33A are connected by thepost structure 32E. Since there should be space for the movingstructures and elements 32A, 32B, 32C, 32D, 32E, 33A, the structure arefabricated with sacrificial layer 37, which will be removed afterfabrication process before operating the device.

Actuation elements 32A, 32B, 32C, 32D, 32E are followed by micromirrorstructure layer 33C including the micromirror structure 33A and dummystructure 33B. The process for building the micromirror structure layer33C is shown in FIG. 3C. Especially the micromirror structure 33A shouldbe the base structure for the optical reflectivity. The structure can beplanarized by applying chemical mechanical polishing process (CMP). TheCMP process can be applied to the over-grown sacrificial layer 37 beforedepositing the micromirror structure 33A or can be applied to themicromirror structure 33A after depositing the micromirror structure 33Ato have flat surface micromirrors for the reflection. While the CMPprocess, it is desirable to have the mechanical structures to beprotected by other structure 33B from the external shock or force. Toprotect the micromirror structure 33A during the CMP process and otherprocesses, the present invention introduces the dummy structures 33B inthe optically non-effective area 39B. The dummy structures 33B arelocated in the optically non-effective area 39B and do not haveactuation elements. The dummy structures 33B are rather fixed structuresthan structures with free moving. The dummy structures 33B in thenon-effective area 39B are fixed and protect the micromirrors in theeffective area 39A from external perturbation. The external perturbationcan be occurred during fabrication of the Micromirror Array Lens andoperation of the Micromirror Array Lens.

The Micromirror Array Lens in the present invention comprises opticallynon-effective area 39B which is other than the controlled micromirrorarea 39A. Since the structure 33B in the non-effective area 39B does notneed actuation parts, the structure 33B of the non-effective area 39B issomewhat different from that 33A of effective area 39A. The structure33B in the optically non-effective area 39B mainly protects themicromirrors 33A in the effective area 39A. Since the Micromirror ArrayLens is a fragile device, the micromirrors 33A in the effective area 39Ashould be protected during the fabrication and the usage. The dummystructures 33B protect the micromirrors 33A in the effective area 39A.The dummy structures 33B encircle the effective area 39A and acts as abuffer area of the device. The dummy structures 33B are also fabricatedwith the micromirror structure 33A or elements 32C, 32D, 32E in theeffective area 39A.

Until now the micromirror structure 33A and the dummy structure 33B arenot separated and the only difference between them is the presence ofthe actuation elements 32C, 32D, 32E. Since the dummy structures 33B donot need to move, the dummy structures 33B do not have movable actuationstructure. The dummy structures 33B rather have the fixed rigidstructures to have rigidity than movable structures. Also the structure33B is not distinguished until the etching process of the micromirrorgap 38 between the micromirror structures 33A and the dummy structures33B.

After depositing the micromirror structure layer 33C, the sub coatinglayer 34C is applied. The process is shown in FIG. 3D. Since the subcoating layer 34C can also be etched together with over coating layer36C and the micromirror structure layer 33C, the layer 34C does not hasany pattern until now, either.

The sub coating 34A encapsulate the metal layer 35 to prevent the metallayer 35 from oxidation and to prevent the micromirror structure 33A andthe actuation elements 32B, 32C, 32D, 32E from galvanic corrosion withthe over coating 36A. The sub coating layer 34C is deposited on themicromirror structure layer 33C with material selected from the groupconsisting of silicon oxide (SiO₂), aluminum oxide (Al₂O₃), magnesiumoxide (MgO), titanium oxide (TiO₂), cesium oxide (CeO₂), silicon nitride(Si₃N₄), titanium nitride (TiN), magnesium fluoride (MgF₂), zinc sulfide(ZnS), zinc selenide (ZnSe), polycarbonate, polyester, polyethylenenaphthalate, and fluoropolymer.

To prevent the micromirror structure 33A and the actuation elements 32B,32C, 32D, 32E from galvanic corrosion, the sub coating layer 34Aprevents the metal layer 35 from electrical contacting with micromirrorstructure 33A. Since the galvanic corrosion can only occur if thedissimilar metals are in electrical contact. Here in the MicromirrorArray Lens, the micromirror structure 33A and the metal layer 35 are thedissimilar metals for possible galvanic corrosion. If the dissimilarmetals are insulated from each other by suitable plastic strips, washersor sleeves then galvanic corrosion cannot occur. Thus the sub coatinglayer 34A prevents the micromirror structure 33A and the actuationelements 32B, 32C, 32D, 32E from galvanic corrosion by electricallyseparating the micromirror structure 33A from the metal layer 35. Thesub coating 34A material should be highly electrically insulating andalso consistent with the fabrication processes.

To have sufficient electrical separation and optical properties, thethickness of the sub coating layer 34C, 34A should be controlled to havebetween 20 nm and 500 nm preferably 100 nm. The sub coating layer 34C,34B is also used for providing anti-reflective coating for the dummystructures 33B in the optically non-effective area 39B. In thenon-effective area 39B, the over coating 36B and the sub coating 34B arecombined together since there is no metal layer. The total thickness ofthe sub coating 34B and the over coating 36B can be controlled to haveanti-reflective property in the non-effective area 39B. Since thethickness of the over coating layer 36C, 36A should be controlled tohave high reflectivity of the metal layer 35, the anti-reflectiveproperty should be obtained by controlling the sub coating layer 34C,34B without providing extra layer structure.

Since the non-effective area 39B should not be optically active, theanti-reflective coating for the non-effective area 39B enhances theperformance of the Micromirror Array Lens. Since the dummy structures33B do not have metal layer, the structure 33B does not have highreflectivity. To enhance the optical performance, it is much better thatthe non-effective area 39B has as low reflectivity as possible. Ananti-reflective coating for the non-effective area 39B is one solution.By controlling the thickness of the existing layers 34C, 34C for themicromirror structures 33A, the non-effective area 39B can haveanti-reflective coating. In the non-effective area 39B, two layers ofsub coating 34B and over coating layers 36B are applied to the dummystructures 33B. The total thickness of the sub coating 34B and overcoating 36B layers can be controlled to have anti-reflective coatingproperties. To provide anti-reflective coating for non-effective area39B along with protection of the metal layer 35 in optically effectivearea 39A is the one of main ideas and advantages of the presentinvention.

In FIG. 3E, the process with the patterned metal layer 35 is presented.The metal layer 35 is patterned with the mask of the micromirror shapes.Only on top of the movable and optically effective area 39A, the metallayer 35 is applied to have high reflectivity. The well known lift-offprocess and evaporation or sputtering process with micro lithography canbe applied to make the metal layer with micromirror patterning.

The metal layer 35 is made of material selected from the groupconsisting of silver (Ag), aluminum (Al), gold (Ag), nickel (Ni),chromium (Cr), and platinum (Pt) to have high reflectivity. Thethickness of the metal layer is controlled to have between 20 nm and1000 nm preferably 100 nm. The thickness should be selected to have highreflectivity of the micromirrors. Also the material of the metal layer35 should be selected by considering the required reflectivity,operating wavelength, operating environment and others. Also since themetal layer 35 is easy to be attacked from acid or base or otherenvironmental reasons, the metal layer 35 should be protected. In thepresent invention, the sub coating layer 34A and the over coating layer36A provide a strong protection for the metal layer 35 from oxidation,acid, base and galvanic corrosion. The over coating layer 36A and thesub coating layer 34A prevent the metal layer 35 from oxidation byencapsulating the metal layer 35. The over coating layer 36A and the subcoating 34A layer protect the metal layer 35 from acid or base tomaintain reflectivity of the micromirror by encapsulating the metallayer 35. Also the over coating layer 36A and the sub coating 34A layerreduces degradation of reflectivity of the micromirrors provided by themetal layer 35. One more thing is that the over coating layer 36A andthe sub coating layer 34A protect the metal layer 35 from etchants whileremoving sacrificial layers 37. Usually while removing sacrificiallayers 37, a strong acid or base such as fluoric acid is applied todissolve the sacrificial layer such as silicon oxide. The protectionfrom a strong acid and a strong base is another purpose of the presentinvention.

Deposition of the over coating layer 36C is illustrated in FIG. 3F. Theover coating layer 36A provides a protection for metal layer 35 from theoperating environments. Since the metal layer 35 should have highreflectivity, the thickness of the over coating layer 36A should becontrolled to maximize reflectivity of the metal layer 35. The maximizedreflectivity enhances the optical performance of the Micromirror ArrayLens. The thickness of the over coating layer 36A is controlled to havebetween 20 nm and 500 nm preferably 100 nm. Since the over coating layer36A is directly exposed to the operating environment, the thickness ofthe over coating layer 36A is more important than that of the subcoating layer 34A, especially to maximize the reflectivity of themicromirrors.

The sub coating layer 34C is deposited on the micromirror structure 33Cwith material selected from the group consisting of silicon oxide(SiO₂), aluminum oxide (Al₂O₃), magnesium oxide (MgO), titanium oxide(TiO₂), cesium oxide (CeO₂), silicon nitride (Si₃N₄), titanium nitride(TiN), magnesium fluoride (MgF₂), zinc sulfide (ZnS), zinc selenide(ZnSe), polycarbonate, polyester, polyethylene naphthalate, andfluoropolymer. The materials for sub coating layer 34C and over coatinglayer 36C can be the same. The material should be selected consideringthe operating environments and the solvent to be used.

FIG. 3G illustrates the etching process of the micromirror device. Themicromirror gap 38 between micromirrors 33A and the dummy structure 33Bis etched. The micromirror structure layer 33C now has its own separatedstructures for micromirrors 33A and dummy structures 33B. TheMicromirror Array Lens comprises optically non-effective area 39B whichis other than the controlled micromirror area 39A. Now the effectivearea 39A and the non-effective area 39B can be differentiated. Since thestructure 33B in the non-effective area 39B does not need actuationparts, the structure 33B of the non-effective area 39B is somewhatdifferent from that 33A of effective area 39A. The non-effective area39B comprises a substrate 31C, at least one dummy structure 33B, a subcoating layer 34B, and an over coating layer 36B. The sub coating 34Band the over coating layers 36B are fabricated together with the layers34A, 36A in the micromirrors in the effective area 39A as one layer 34C,and 36C.

Since the Micromirror Array Lens is a fragile device, the micromirrorsshould be protected during the fabrication and the usage. The structuresin non-effective area 39B protect the micromirror structures 33A in theeffective area 39A. The dummy structures 33B encircle the effective area39A and act as a buffer area 39B of the device. The dummy structures 33Bare also fabricated with the micromirror structure 33A or elements 32C,32D, 32E in the effective area 39A.

The non-effective area 39B should not be optically active. Theanti-reflective coating enhances the performance of the MicromirrorArray Lens. Since the dummy structures 33B do not have metal layer 35,the structure 33B does not have high reflectivity. To enhance theoptical performance, it is much better that the non-effective area 39Bhas as low reflectivity as possible. An anti-reflective coating for thenon-effective area 39B is one solution. By controlling the thickness ofthe existing layers 34C, 36C for the micromirrors, the non-effectivearea 39B can have anti-reflective coating. In the non-effective area39B, two layers of sub coating 34B and over coating 36B layers areapplied to the dummy structures 33B. The total thickness of the subcoating 34B and over coating 36B layers can be controlled to haveanti-reflective coating properties. To provide anti-reflective coatingfor non-effective area 39B along with protection of the metal layer 35is the one of main ideas and advantages of the present invention.

In FIG. 3H, the released structure of the Micromirror Array Lens withoutthe sacrificial layer 37 is shown. Since there should be space for themoving structures and elements 32B, 32C, 32D, 32E, the structures forthe Micromirror Array Lens are fabricated with sacrificial layer 37,which will be removed after fabrication process before operating thedevice. Usually while removing sacrificial layers 37, a strong acid orbase such as fluoric acid is applied to dissolve the sacrificial layers37 such as silicon oxide. After removing the sacrificial layers 37, theMicromirror Array Lens is ready for usage.

In FIG. 3I, the Micromirror Array Lens which has the same material forthe sub coating 34A, 34B and the over coating 36A, 36B in the structure.Since the material of the sub coating 34A, 34B and the over coating 36A,36B is the same. The process for the Micromirror Array Lens can madesimplified and compact. The thickness of the over coating 36A, 36B layershould be determined by considering the optical reflectivity of themetal layer 35 in the effective area 39A. And the thickness of the subcoating 34A, 34B layer should be determined by considering theanti-reflective property of the dummy structures 33B in the opticallynon-effective area 39B. By controlling both the thicknesses of the subcoating 34A, 34B layer and the over coating 36A, 36B layer, theprotection with high reflectivity for the metal layer 35 and theanti-reflection for the dummy structures 33B can be obtainedsimultaneously. The present invention has superior advantages of havinghigh reflectivity for the metal layer 35 and the anti-reflection for thedummy structures 33B simultaneously. Also the process does not use extralayer or structure for making the Micromirror Array Lens.

FIG. 4 shows an example of Micromirror Array Lens application geometry.The incident light 46 comes from the left and passes through anauxiliary lens 45. The auxiliary lens 45 changes optical power of thesystem. Then the Micromirror Array Lens 41 changes the focal length,optical axis and other focusing properties of the optical system to makeimages 44 onto the image sensor 43 by controlling each micromirror 42 inthe Micromirror Array Lens 41 independently. In this geometry, theMicromirror Array Lens 41 has an axis-symmetry about the y-axis. Thecoordinate configuration is shown in the figure. Since the system has anaxis-symmetry, the shape of the micromirror 42 can be determined byconsidering the axis-symmetry of the optical system. To have anautomatic function, the control process of the Micromirror Array Lens 41according to the image quality on the image sensor 43 should be added.

The shape of the micromirrors 42 can be varied with geometry of theMicromirror Array Lens 41. The micromirrors 42 in the effective areahave a shape selected from the group consisting of fan, rectangular,square, hexagonal, and triangular shapes. For an optical system with anaxis-symmetry such as shown in FIG. 4, the micromirrors with rectangularor square shapes can be selected to have a proper geometry of theoptical system. The hexagonal and triangular shape micromirrors are alsoused for systems with the axis-symmetry, especially with three-fold axissymmetry. Hexagonal micromirrors can be used for highly dense system.Anyway, the selection of the micromirror shapes is highly dependent onthe optical system geometry and the devices.

In FIG. 5, an example of the Micromirror Array Lens 51 is shown for theaxis-symmetry system shown in FIG. 4. The coordinate of the MicromirrorArray Lens is the same as the one in FIG. 4. There can be found theoptically effective area 54 in the center and also the opticallynon-effective area 55 can be found around the effective area 54. Thenon-effective area 55 has a plurality of dummy structures 53 to protectthe micromirrors 52 in the effective area 54. And since the opticalsystem has an axis-symmetry about y-axis, the Micromirror Array Lens 51has also an axis-symmetry about the y-axis. The micromirrors 52 in theoptically effective area 54 only make their own motion to build anoptical surface profile. The optical surface profile satisfiesconvergence and phase matching conditions for forming a lens.

To have a function as a Micromirror Array Lens, the micromirror arrayfor the Micromirror Array Lens should satisfy two conditions to form agood lens. One is the convergence condition that every light should beconverged into a focal point. The other is the phase matching conditionthat the phase of the converged light should be the same. In aconventional lens, the phase matching condition is that all the lightpassing through a lens should have the same optical path length to thefocal point. But the Micromirror Array Lens arranged in a flat surfaceuses the periodicity of the light to satisfy the phase matchingcondition. Since the same phase condition occurs periodically, the phasematching condition can be satisfied even though the optical path lengthis different. Each micromirror in the Micromirror Array Lens can becontrolled independently to satisfy the phase matching condition and theconvergence condition.

Only after satisfying the convergence and the phase matching conditions,the Micromirror Array Lens can build a lens with an optical surfaceprofile. An optical surface profile is the surface shape of themicromirror array which meets the lens conditions of convergence andphase matching. Each micromirror in the effective area is independentlycontrolled to form at least an optical surface profile. The MicromirrorArray Lens has a plurality of optical surface profiles to have avariable focusing property. By changing the optical surface profiles,the Micromirror Array Lens can change its focal length, optical axis,and other focusing properties. The Micromirror Array Lens can be avariable focusing lens having lots of optical surface profiles. Forhaving an automatic focusing function, the system can havepre-determined optical surface profiles according to the objectdistance. The different optical surface profiles are controlled with thesignal from the image sensor.

FIG. 6 shows another example of the Micromirror Array Lens 64application geometry. The incident light 61 comes from the left andpasses through an auxiliary lens 62. The auxiliary lens 62 changesoptical power of the system. Then cube beam splitter 63 change theincident light 61 direction down to the Micromirror Array Lens 64. TheMicromirror Array Lens 64 changes the focusing properties of the opticalsystem to make images 67 onto the image sensor 66 by controlling eachmicromirror 65 in the Micromirror Array Lens 64 independently. In thisgeometry, the Micromirror Array Lens 64 has a rotational symmetry aboutthe center of the Micromirror Array Lens 64. Since the system has arotational symmetry, the shape of the micromirror 65 can be determinedby considering the rotational symmetry of the optical system. With anoptical geometry with a rotational symmetry such as shown in FIG. 6, themicromirrors 65 with a fan shape can be used as a good candidate foreffective unit micromirror for making a Micromirror Array Lenses 64. Thehexagonal and triangular shape micromirrors can also be used for systemwith a rotational symmetry. Hexagonal micromirrors can be used forhighly-dense system. Anyway the selection of the micromirror shape ishighly dependent on the optical system geometry and the devices.

In FIG. 7, another example of the Micromirror Array Lens 71 is shown forthe rotation symmetry system shown in FIG. 7. There can be found theoptically effective area 74 in the center and also the opticallynon-effective area 75 can be found around the effective area 74. Thenon-effective area 75 has two dummy structures 73 encircled theeffective area 74 to protect the micromirrors 72 in the effective area74. And since the optical system has a rotational symmetry about thecenter, the Micromirror Array Lens 71 has also a rotational symmetryabout the center. The micromirrors 72 with a fan shape are used for theMicromirror Array Lenses 71.

While the invention has been shown and described with reference todifferent embodiments thereof, it will be appreciated by those skills inthe art that variations in form, detail, compositions and operation maybe made without departing from the spirit and scope of the presentinvention as defined by the accompanying claims.

1. A Micromirror Array Lens having a plurality of micromirrors, whereineach micromirror in optically effective area comprising: a) a substratewith at least one electrode to provide actuation force for micromirrormotion; b) at least one actuation element to make micromirror motioncontrolled by electrostatic force induced by the electrodes in thesubstrate; c) a micromirror structure having rotational and/ortranslational motions controlled by the actuation elements; d) a subcoating layer; e) a metal layer to make the micromirror structure havehigh reflectivity; and f) an over coating layer to encapsulate the metallayer with the sub coating layer; wherein the effective area is wherefocusing of the Micromirror Array Lens occurs and wherein the metallayer is encapsulated by the sub coating layer and the over coatinglayer to prevent the metal layer from oxidation and to prevent themicromirror structure and the actuation elements from galvaniccorrosion.
 2. The Micromirror Array Lens of claim 1, wherein themicromirrors in the effective area have a shape selected from the groupconsisting of fan, rectangular, square, hexagonal, and triangularshapes.
 3. The Micromirror Array Lens of claim 1, wherein the substratefurther comprises a control circuitry constructed by using semiconductormicroelectronics technologies.
 4. The Micromirror Array Lens of claim 1,wherein the electrodes are protected by passivation layer wherein thepassivation layer prevents the electrodes from possible electric contactwith the actuation elements or the micromirror structure.
 5. TheMicromirror Array Lens of claim 1, wherein each micromirror in theeffective area is independently controlled to form at least an opticalsurface profile.
 6. The Micromirror Array Lens of claim 5, wherein themicromirrors in the effective area are controlled by a common inputsignal to the electrodes to form an optical surface profile.
 7. TheMicromirror Array Lens of claim 5, wherein the Micromirror Array Lenshas a plurality of optical surface profiles to have a variable focusingproperty.
 8. The Micromirror Array Lens of claim 1, wherein the subcoating layer is deposited on the micromirror structure with materialselected from the group consisting of silicon oxide (SiO₂), aluminumoxide (Al₂O₃), magnesium oxide (MgO), titanium oxide (TiO₂), cesiumoxide (CeO₂), silicon nitride (Si₃N₄), titanium nitride (TiN), magnesiumfluoride (MgF₂), zinc sulfide (ZnS), zinc selenide (ZnSe),polycarbonate, polyester, polyethylene naphthalate, and fluoropolymer.9. The Micromirror Array Lens of claim 1, wherein the sub coating layerprevents the metal layer from electrical contacting with the micromirrorstructure.
 10. The Micromirror Array Lens of claim 1, wherein the subcoating layer prevents the micromirror structure and the actuationelements from galvanic corrosion by electrically separating themicromirror structure from the metal layer.
 11. The Micromirror ArrayLens of claim 1, wherein thickness of the sub coating layer iscontrolled to have between 20 nm and 500 nm preferably 100 nm.
 12. TheMicromirror Array Lens of claim 1, wherein the metal layer is made ofmaterial selected from the group consisting of silver (Ag), aluminum(Al), gold (Au), nickel (Ni.), chromium (Cr), and platinum (Pt) to havehigh reflectivity.
 13. The Micromirror Array Lens of claim 1, whereinthickness of the metal layer is controlled to have between 20 nm and1000 nm preferably 100 nm.
 14. The Micromirror Array Lens of claim 1,wherein the over coating layer is deposited on the micromirror structurewith material selected from the group consisting of silicon oxide(SiO₂), aluminum oxide (Al₂O₃), magnesium oxide (MgO), titanium oxide(TiO₂), cesium oxide (CeO₂), silicon nitride (Si₃N₄), titanium nitride(TiN), magnesium fluoride (MgF₂), zinc sulfide (ZnS), zinc selenide(ZnSe), polycarbonate, polyester, polyethylene naphthalate, andfluoropolymer.
 15. The Micromirror Array Lens of claim 1, whereinthickness of the over coating layer is controlled to maximizereflectivity of the metal layer.
 16. The Micromirror Array Lens of claim1, wherein thickness of the over coating layer is controlled to havebetween 20 nm and 500 nm preferably 100 nm.
 17. The Micromirror ArrayLens of claim 1, wherein the over coating layer and the sub coatinglayer prevent the metal layer from oxidation by encapsulating the metallayer.
 18. The Micromirror Array Lens of claim 1, wherein the overcoating layer and the sub coating layer protect the metal layer fromacid and base to maintain reflectivity of the micromirror byencapsulating the metal layer.
 19. The Micromirror Array Lens of claim1, wherein the over coating layer and the sub coating layer protect themetal layer from etchants while removing sacrificial layers.
 20. TheMicromirror Array Lens of claim 1, wherein the over coating layer andthe sub coating layer protect the metal layer from degradation ofreflectivity of the metal layer.
 21. The Micromirror Array Lens of claim1, wherein the Micromirror Array Lens further comprises opticallynon-effective area wherein the non-effective area comprises: a) asubstrate; b) at least one dummy structure; c) a sub coating layer; andd) an over coating layer; wherein the sub coating and the over coatinglayers are fabricated together with the layers in the micromirrors inthe effective area.
 22. The Micromirror Array Lens of claim 21, whereinthe dummy structures in the non-effective area are fixed and protect themicromirrors in the effective area from external perturbation.
 23. TheMicromirror Array Lens of claim 21, wherein total thickness of the subcoating layer and the over coating layer is controlled to haveanti-reflective property of the dummy structures.
 24. A MicromirrorArray Lens comprising: an optically effective area with a plurality ofmicromirrors, wherein the micromirrors in the effective area comprising:a) a substrate with at least one electrode to provide actuation forcefor micromirror motion; b) at least one actuation element to makemicromirror motion controlled by the electrostatic force induced by theelectrodes in the substrate; c) a micromirror structure havingrotational and translational motions controlled by the actuationelements; d) a sub coating layer; e) a metal layer to make themicromirror structure have high reflectivity; and f) an over coatinglayer to encapsulate the metal layer with the sub coating layer; whereinthe effective area is where focusing of the Micromirror Array Lensoccurs and wherein the metal layer is encapsulated by the sub coatinglayer and the over coating layer to prevent the metal layer fromoxidation and to prevent the micromirror structure and the actuationelements from galvanic corrosion; and an optically non-effective areawherein the non-effective area comprises: a) a substrate; b) at leastone dummy structure; c) a sub coating layer; and d) an over coatinglayer; wherein the sub coating and the over coating layers arefabricated together with the layers in the micromirrors in the effectivearea.
 25. The Micromirror Array Lens of claim 24, wherein themicromirrors in the effective area have a shape selected from the groupconsisting of fan, rectangular, square, hexagonal, and triangularshapes.
 26. The Micromirror Array Lens of claim 24, wherein thesubstrate further comprises a control circuitry constructed by usingsemiconductor microelectronics technologies.
 27. The Micromirror ArrayLens of claim 24, wherein the electrodes are protected by passivationlayer wherein the passivation layer prevents the electrodes frompossible electric contact with the actuation elements or the micromirrorstructure.
 28. The Micromirror Array Lens of claim 24, wherein eachmicromirror in the effective area is independently controlled to form atleast an optical surface profile.
 29. The Micromirror Array Lens ofclaim 28, wherein the micromirrors in the effective area are controlledby a common input signal to the electrodes to form an optical surfaceprofile.
 30. The Micromirror Array Lens of claim 28, wherein theMicromirror Array Lens has a plurality of optical surface profiles tohave a variable focusing property.
 31. The Micromirror Array Lens ofclaim 24, wherein the sub coating layer is deposited on the micromirrorstructure with material selected from the group consisting of siliconoxide (SiO₂), aluminum oxide (Al₂O₃), magnesium oxide (MgO), titaniumoxide (TiO₂), cesium oxide (CeO₂), silicon nitride (Si₃N₄), titaniumnitride (TiN), magnesium fluoride (MgF₂), zinc sulfide (ZnS), zincselenide (ZnSe), polycarbonate, polyester, polyethylene naphthalate, andfluoropolymer.
 32. The Micromirror Array Lens of claim 24, wherein thesub coating layer prevents the metal layer from electrical contactingwith the micromirror structure.
 33. The Micromirror Array Lens of claim24, wherein the sub coating layer prevents the micromirror structure andthe actuation elements from galvanic corrosion by electricallyseparating the micromirror structure and the metal layer.
 34. TheMicromirror Array Lens of claim 24, wherein thickness of the sub coatinglayer is controlled to have between 20 nm and 500 nm preferably 100 nm.35. The Micromirror Array Lens of claim 24, wherein the metal layer ismade of material selected from the group consisting of silver (Ag),aluminum (Al), gold (Au), nickel (Ni.), chromium (Cr), and platinum (Pt)to have high reflectivity.
 36. The Micromirror Array Lens of claim 24,wherein thickness of the metal layer is controlled to have between 20 nmand 1000 nm preferably 100 nm.
 37. The Micromirror Array Lens of claim24, wherein the over coating layer is deposited on the micromirrorstructure with material selected from the group consisting of siliconoxide (SiO₂), aluminum oxide (Al₂O₃), magnesium oxide (MgO), titaniumoxide (TiO₂), cesium oxide (CeO₂), silicon nitride (Si₃N₄), titaniumnitride (TiN), magnesium fluoride (MgF₂), zinc sulfide (ZnS), zincselenide (ZnSe), polycarbonate, polyester, polyethylene naphthalate, andfluoropolymer.
 38. The Micromirror Array Lens of claim 24, whereinthickness of the over coating layer is controlled to maximizereflectivity of the metal layer.
 39. The Micromirror Array Lens of claim24, wherein thickness of the over coating layer is controlled to havebetween 20 nm and 500 nm preferably 100 nm.
 40. The Micromirror ArrayLens of claim 24, wherein the over coating layer and the sub coatinglayer prevent the metal layer from oxidation by encapsulating the metallayer.
 41. The Micromirror Array Lens of claim 24, wherein the overcoating layer and the sub coating layer protect the metal layer fromacid and base to maintain reflectivity of the micromirror byencapsulating the metal layer.
 42. The Micromirror Array Lens of claim24, wherein the over coating layer and the sub coating layer protect themetal layer from etchants while removing sacrificial layers.
 43. TheMicromirror Array Lens of claim 24, wherein thicknesses of the subcoating layer and the over coating layer are controlled to haveanti-reflective property of the dummy structures.
 44. A method formaking a Micromirror Array Lens, comprising: a) forming electrodes andcontrol circuitry on a substrate; b) building micromirror actuationelements with sacrificial layer or layers; c) applying a micromirrorstructure layer; d) applying a sub coating layer to the micromirrorstructure; e) applying a metal layer to the sub coating layer oneffective area; f) applying an over coating layer; g) selectivelyetching the sub coating layer, the over coating layer and themicromirror structure layer to make micromirror structures; h) removingthe sacrificial layers and releasing the actuation elements and themicromirror structures. wherein the effective area is where focusing ofthe Micromirror Array Lens occurs and wherein the metal layer isencapsulated by the sub coating layer and the over coating layer toprevent the metal layer from oxidation and to prevent the micromirrorstructures and the actuation elements from galvanic corrosion.
 45. Themethod for making the Micromirror Array Lens of claim 44, whereinfurther comprises a step for building a passivation layer beforebuilding the micromirror actuation elements with the sacrificial layers.